1. Field of the Invention
The present invention relates to an optical pickup actuator for improving a coil winding structure of a lens holder.
2. Description of the Background Art
Optical pickup actuator refers to a device for recording information or reproducing the recorded information following an optical recording medium. The optical pickup actuator constantly maintains a relative position between an objective lens and the optical recording medium by moving a lens holder for holding the objective lens.
FIGS. 1 to 3 are views illustrating a conventional optical pickup actuator.
The optical pickup actuator 100 includes a lens holder 102 for holding an objective lens at its center; and a magnetic circuit disposed at one side of the lens holder 102 and activating the lens holder 102.
The magnetic circuit includes focusing coils 104, tracking coils 105, a yoke 107, and multipolar magnets 110a to 110d. 
The focusing coils 104 are disposed at the left and right of both side surfaces of the lens holder 102 to perform focusing operations. The focusing coil 104 is positioned to face a horizontal boundary 111 between magnets having different polarities.
The tracking coils 105 are disposed at the centers of both side surfaces of the lens holder 102 to perform tracking operations. The tracking coil 105 is positioned to face a vertical boundary 112 between magnets having different polarities.
The radial coil 103 is disposed at an upper side of the lens holder 102 to perform a radial tilting operation. The radial coil 103 is disposed at a circumference surface of the lens holder 102. A portion of the radial coil 103 is positioned to face the vertical boundary 112 between the magnets having the different polarities.
The multipolar magnets are comprised of rectangular magnets 110c and 110d disposed at their lower sides, and rectangular magnets 110a and 110b disposed at upper sides of and between the magnets 110c and 110d. 
The magnets 110a to 110d are respectively fixed to an inner surface of the yoke 107, which is formed of ferromagnetic substance and disposed adjacently to the lens holder 102. The yoke 107 functions as a path for magnetic fields generated from the magnets 110a to 110d. 
Wire suspensions 106 are fixed at their one ends to both side surfaces of the lens holder 102, and fixed at their other ends to a frame provided at one side of the lens holder 102. The wire suspension 106 supports the lens holder 102, and supplies electric current.
An operation of the optical pickup actuator 100 will be described as follows.
When electric current flows through the focusing coil 104, the focusing coil 104 is interacted with the magnetic field generated from the horizontal boundary 111 between the facing magnets and is vertically forced due to the interaction, thereby activating a focusing servo.
When the electric current flows through the tracking coil 105, the tracking coil 105 is interacted with the magnetic field generated from the vertical boundary 112 between the facing magnets and is horizontally forced due to the interaction, thereby activating a tracking servo.
When the electric current flows through the radial coil 103, the radial coil 103 is interacted with the magnetic field generated from the horizontal boundary 111 between the facing magnets and is forced upward and downward due to the interaction, thereby performing the radial tilting operation.
As shown in FIG. 2, the radial tilting operation refers to the operation of forcing the lens holder 102 upward at one side and downward at the other side, thereby rotating the lens holder 102.
In the optical pickup actuator 100, the lens holder 102 is moved using an interaction between the magnet and the coil, thereby minimizing error of a light signal.
However, the conventional optical pickup actuator 100 has a drawback in that it requires a structure for winding the radial coil 103 on the lens holder 102, and a separate process for winding the radial coil 103.